1. Field of the Invention
The invention relates to an apparatus for preparing and pouring unit doses of extraction beverages such as coffee or tea, comprising
a filter unit with means for advancing a strip of filter paper over a fixed filter position,
an upwardly and downwardly moveable extraction chamber, located above the filter position, with an at least partly open bottom, and provided at the topside with supply means for supplying doses of extraction agent, such as ground coffee or tea, and hot water,
a collection chamber fixedly located under the filter position, of which the open top side, which is covered by a grating or perforated plate abuts the filter paper on the filter position, and to which a pouring spout, provided with a valve, is connected at the underside,
a pressure control means for regulating the air pressure in the collection chamber, and
driving means for driving the apparatus in a coordinated way for performing a working cycle, in which
in a first phase, during which the bottom edge of the extraction chamber is pressed against the filter position and extraction agent and hot water are introduced in the extraction chamber through the respective feeds,
in a second phase air is pressed from the collection chamber through the filter paper into the extraction chamber,
in a third phase the brewed extract is suctioned through the filter paper to the collection chamber, and
in a fourth phase the valve of the pouring spout is opened, the extraction chamber is moved upwards, and the strip of filter paper is advanced.
2. Description of Related Art
Such apparatus are known and are used in particular as automatic coffee or tea vending machines and are generally part of more extensive automatic beverage dispensers, from which other beverages also are available.
Such an apparatus is known from several publications, including international application WO-A-91/01673. In this known device the air pressure in the collection chamber is regulated by a driven double action pump, of which the pump line is connected to the side wall of the collection chamber above the highest level attainable by the extraction fluid suctioned into it. There is a fluid outlet at the centre of the bottom of the collection chamber, which serves as a pouring spout and which is provided with a valve.
In this known device an electronic circuit ensures that the various elements can work in a coordinated manner. For preparing a cup of extraction beverage, e.g. a cup of coffee, when the extraction chamber is pressed against the filter, and coffee grindings and hot water have been provided therein, the pump is switched to blowing, in which air is blown into the collection chamber, which, as a result of the overpressure created, penetrates through the filter into the extraction chamber and thereby causing an advantageous mixing action, by which extraction agent (coffee) and hot water contact each other intimately, which allows a good extraction.
After this extraction phase the pump is switched to suctioning, by which, as a result of the underpressure created in the collection chamber, the extraction fluid is suctioned from the extraction chamber through the filter into the collection chamber. Finally, the last phase occurs, in which the valve of the pouring spout is opened and the coffee is poured.
This known device functions well and purposively for providing unit doses of extraction beverages such as coffee, but has the disadvantage that the double action pump is an expensive element, and further that it is expensive in terms of power consumption. There is further the possibility that the extraction fluid, drawn through the filter during the suctioning phase, is being suctioned partly into the pump line when coming down, which entails a risk of damaging the expensive pump installation.